When a terminal product is inserted into a power supply port, an instant power-on inrush current will be generated at the power supply port as a filter capacitor of an input end of the power supply of the terminal product needs to draw a large amount of instant current to establish a voltage, which causes the voltage at the power supply port to drop instantly, thereby influencing the stability of the power supply system.
In order to maintain the stability of the power supply system, a soft start circuit will generally be added at the input side of the power supply of the terminal product in the related technologies, to reduce the impact on the power supply due to the power-on of the terminal. The soft start circuit is generally followed by a DCDC circuit. In order to deal with a large spike-type load current, the input end of the DCDC circuit will generally have an energy-storage capacitor with a large capacity.
In the related technologies, there are mainly the following problems: when the terminal product is plugged quickly, the discharge of the input capacitor with a large capacity of the DCDC will be very slow, which results in the voltage of the back end of the soft start circuit dropping slowly, and when the terminal product is powered on again quickly, a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) transistor of the soft start circuit may be still in a direct on-state, which causes the soft start circuit to be ineffective. If the soft start circuit is not in use, the power-on inrush voltage and the inrush current will impact the device of the back end of the soft start circuit directly, which results in a damage of the device.